1. Field of the Invention
The present invention relates to a powder and granular material crushing and sizing apparatus for sizing, to a predetermined particle size, various wet or dry materials such as pharmaceuticals, foodstuffs, fodder, chemicals, fertilizers, powdered coal, limestone or ceramics materials that are granulated or formed by various apparatuses. More particularly, the present invention relates to a powder and granular material crushing and sizing apparatus that crushes granules (lumps) of a target particle size or greater, such as wet aggregates or dry blocks granulated or formed by various apparatuses, and that sizes the granules within a given particle size range.
2. Description of the Related Art
Mixing, granulating and sizing operations of powder and granular materials are widely carried out in numerous industrial fields, such as in the pharmaceutical and food industries. Particle size adjustment is an important unit operation in production processes, with a view to, for instance, improving the quality of the powder and granular material, increasing fluidity during fluidized drying, and improving handling. A crushing and sizing apparatus is used for the above particle size adjustment operation.
The applicant has disclosed such a powder and granular material crushing and sizing apparatus in Japanese Patent No. 4113222.
The powder and granular material crushing and sizing apparatus comprises a plurality of disc-like rotors fixedly supported, at intervals, by a drive shaft provided in a horizontal direction; and a plurality of semi-circular arc stators provided below the disc-like rotors and that oppose disc faces of the peripheral edge thereof, the stators having inclined faces such that the gap between the stators and the disc faces of the disc-like rotors becomes narrower towards the peripheral edges of the disc-like rotors; wherein the disc faces of the disc-like rotors and the inclined faces of the stators form hopper-like gap portions where a powder and granular material is held, and wherein the narrowest gap portions between the peripheral edges of the disc-like rotors and the stators form crushing and sizing sections.
In the above powder and granular material crushing and sizing apparatus, the powder and granular material to be processed is fed, from above the disc-like rotors, to the gap portions that are delimited by the peripheral-edge disc faces of the disc-like rotors and the inclined faces of the stators. The powder and granular material is crushed and sized at the narrowest gap portions and is discharged downwards.
In the above powder and granular material crushing and sizing apparatus, the disc-like rotors and the stators had to be disassembled to be cleaned. However, the structure of the apparatus is such that the plurality of stators is assembled, interposing spacers between the disc-like rotors, to a plurality of fixed shafts disposed across the interior of a casing. Therefore, removal and mounting of the stators was cumbersome. To replace the disc-like rotors, moreover, it was necessary to remove first a powder and granular material charging casing and a casing main body, remove next a belt from a pulley, remove a drive shaft, with the disc-like rotors fixed thereto, from the bearing that holds the drive shaft, and remove thereafter the disc-like rotors from the drive shaft. To mount the disc-like rotors, the above procedure had to be carried out in reverse order, which made for a cumbersome removal and mounting of the disc-like rotors.